There has been an image display device that adopts an object-tracking technique that uses moving images working together with graphics. The object-tracking technique is a technique of detecting the location of an object on a moving image and the like when the object on the moving image is tracked, generating for example a tracking image in the shape of a rectangle at the detected location, and displaying the moving and tracking images that are superimposed on each other. It is known that the object-tracking technique is for example applied to a vehicle detection technique. The vehicle detection technique is a technique of detecting a vehicle with the use of an on-vehicle camera and drawing a figure showing a result of the tracking of the vehicle.
However, it is after an image processing unit detects the location of the object and the like for each frame of the moving image that a drawing unit draws the tracking image on the basis of a result of the detection. Therefore, the number of times the image processing unit notifies the drawing unit of the result of the object detection increases, putting more burden on the image display device. It is possible to reduce burden on the image display device by detecting the location of the object and the like after a process of thinning out the frames and then drawing the tracking image on the basis of the result of the detection. In this case, however, the problem is that the tracking images are not seamlessly displayed but are spaced out when being displayed.